Electronic coupling to parallel vacuum tubes



g .21, 1956 c. s. POWELL, JR 7 2,760,010

ELECTRONIC COUPLING TO PARALLEL VACUUM TUBES Filed Aug. 5, 1952 IN VEN TOR.

ATTORNEY ELECTRONIC COUPLING TO PARALLEL VACUUM TUBES Charles S. Powell, Jr., Jenkintown, Pa. Application August 5, 1952, Serial No; 302,856 8 Claims. (Cl. 179-171) (Granted under Title 35, U. s. Code 1952 sec. 266) The invention described herein may be manufactured and used by, or for, the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor This invention relates to a method and apparatus for ing and positioning of the elements in the course of manufacture. It is impractical, from a manufacturing standpoint to attempt to hold tolerances to zero, and therefore, thermionic tubes of the same type number may. exhibit variations as high as 30% in certain operating characteristics. Where tubes are employed in a parallel or divided circuit, appreciable differences in operating characteristics result in a reduction in the efficiency of the circuit and also place an undue strain on one component. In circuits requiring a close balance, it has been necessary to employ utmost care in selecting matched tubes. Such selection requires time consuming and painstaking testing of large numbers of tubes. In view of.the costliness of such matching and where the time factor did not permit such selection, the user was forcedto operate the circuit without matching tubes at a lower efliciency and also a reduction in tube life.

The principal object of this invention is to provide means for varying the input to parallel tubes in a radio frequency circuit so as to compensate for dififerences in tube characteristics.

Another purpose of this invention is to provide means for applying ultra-high frequency driving power from a single power source to the grid elements of parallel vacuu-m tubes whereby the input to the individual tubes may be varied to compensate for differences in the tube characteristics. a

A further purpose of my invention is to provide means for varying the input circuit in an ultra-high frequency parallel tube circuit whereby the input to the individual tubes may be varied to compensate for circuit differences and slight differences in positioninglof the tubes.

A further object of this invention is to provide means for applying driving power from a single power source to the grid elements of parallel vacuum tubes in an ultrahigh frequency cavity type amplifier whereby the input to the tubes may be varied to compensate for variations in tube characteristics and slight differences in positioning of the tubes withina cavity. i g

A further aim of the invention is to provide mechanically adjustable means between the grid driving coaxial cable, parallel line, or other input means and the grid terminals of a pair of like tubesto compensate for manufacturing tolerances and to permit balancing of any two tubes of a designed type.

Further objects and advantages of the invention will 2,760,010 Patented Aug. 21, 1956 become apparent from the following description and claims and from the accompanying drawing wherein:

Fig. 1 is a side elevational view of a portion of a cavity resonator or amplifier illustrating the input means of the present invention.

Fig. 2 is an elevational view taken at right angles to Fig. 1.

Fig. 3 is a plan view of a modification of the input means.

Fig. 4 is a side elevational view of the input means of Fig. 3 with the tube terminals removed for purposes of clarity. 1

Fig. 5 is a plan'view of a further form of the input means of this invention.

The invention contemplates providing an input means for a divided electronic circuit whereby the input to each portion may be governed so as to produce substantially equal outputs from each division of the circuit. It is understood of course that the input means of the modificationsshown in Figs. 3 and 4 and in Fig. 5 may readily be applied to a cavity resonator or amplifier in the same manner as illustrated in Fig, 1 and Fig. 2 and that insulating material may be disposed on the device of Fig. 5 in the manner shown in Figs. 1-4 inclusive.

Referring to the drawings, and in particular to Fig. 1

. and Fig. 2, a coaxial cable, parallel line, or other highfrequency input means 8 impresses a high-frequency signal upon conductor 7. Analyzing arm 1 is pivotally supported on conductor 7 by means of locking screw 2. The free end of analyzing arm 1 is slidably disposed on coupling strap 3 which, in turn, is connected at its end portions to the grid pins 4 of tubes 5 of a parallel tube circuit. An insulating sheet 6, such as mica or the like, may be interposed between coupling strap 3 and the free. end of the analyzing arm. 1. if it desirable to isolate direct current at this point. Analyzing arm 1 is outwardly bowed between its bearing end surface to form a flat spring contact element 9 which makes sliding contact with the insulating sheet 6 or with the coupling strap 3 if theinsulating sheet 6 is not used. The conductor, analyzing arm and coupling strap are preferably made of flat sheet metal stock to minimize losses due to skin effects. Efiiciency of transmission may be maintained at a maximum by the use of conductors of low resistance, flat sheet metal stock and large surface area.

Behavior of radio wave energy at ultra-high frequencies is difficult topredict. According to conventional direct. or alternating current theory, a voltage is developed across an input resistance or impedance as current flows through the resistance or impedance and the amount of voltage developed with respect to a ground or reference point will .be directly proportional to the resistance or impedance.

In the case of ultra-high frequency power, development is believed to take place across the input impedance. However, the physical structure of input impedance is somewhat different than it is' in the case of the lower frequencies, and its precise nature is diflicult to determine. A length of wire or a strip of material may, it is believed, act as an inductance or capacitance at these frequencies. Therefore, varying the material or physical dimensions of the input components may considerably alter the reactances and hence the impedance of such a Therefore, by rotating sliding analyzing arm 1 to right or left of center position, as .shown by the broken lines in Fig. 2, the impedance and hence the radio frequency driving power developed, may be divided in any manner between the two tubes. In that way, the power may be distributed to the two components so as to compensate for differences in tube characteristics as well as for variations in the positioning of the tubes within a cavity.

The free end of the analyzing arm 1 is adjusted to an optimum point, that is, to a position at which the output power of each tube is substantially identical to that of the other tube. Under such operating conditions, tube life as well as operating efficiency of the amplifier, will be at a maximum.

A modified and alternative structure is shown in Figs. 3 and 4. In this modification, radio frequency driving power is introduced through conductor 10. An analyzing arm 11 pivotally attached to conductor by means of locking screw 12 carries the radio frequency power to arcuate coupling strap 13 from whence it is transmitted to the tube terminals 14.

Analyzing arm 11 slidably contacts arcuate coupling strap 13 and is attached thereto by means of locking screw 16 which rides in elongated arcuate slot 15. The looking screw serves to secure analyzing arm 11 in any desired position along the slot. Thus, analyzing arm 11 may be pivoted on the axis of locking screw 12 and secured in position at any desired point along slot 15. A radio frequency insulating yoke member 17 is secured at its apex to conductor 10 by means of locking screw 12. The free ends of the yoke member 17 support arcuate coupling strap 13. A nut 18 preferably formed of insulating material is threaded upon the locking screw 12 to provide means for fixedly securing the yoke and analyzing arm to conductor 10.

Fig. 5 illustrates a further modification of the coupling means of this invention wherein the input path length to each tube or component may be varied independently of the path length to the other tube or component.

The coupling means includes a Y-shaped driving member 20 adapted to be secured to the radio frequency driving power source. The Y-shaped driving member consists of an elongated conductor 21 which terminates in a transverse bar 22. Arcuate projecting legs 23 and 24 are secured to the ends of the transverse bar or the legs may be integral with the transverse bar. Each of the legs 23 and 24 is provided with an arcuate slot 25 and 26, re-' spectively, which extends substantially the length of its respective leg. Analyzer arms 27 and 28 are secured to the arcuate legs 23 and 24, respectively, the arms extending radially from the legs and are adapted to be connected to the grid terminals of the two tubes. The analyzer arms 27 and 28 are secured to their respective legs by means of locking screws 29 and 30, respectively, which extend through The analyzer arms may thereby be fixedly secured to their respective legs at any desired position along the length of the legs.

In the use of this form of coupling means, the positions of the analyzing arms are adjusted along their respective supporting legs to determine peak output from each of the tubes. In making these adjustments, the analyzing arms are pivoted using the grid terminals or connections as a center of rotation. By successive adjustments of the analyzer arms, the analyzer arm associated with the weaker tube is positioned on the arcuate leg to produce maximum output from this tube. The analyzer arm associated with the other tube is positioned on its arcuate leg so as to produce a matched output. Thus, both balanced output and maximum output may be obtained.

It will be apparent that the adjustable couplings shown are merely illustrative embodiments of my invention and that variations thereof will readily occur to one skilled in the art. The invention is not restricted to use with the respective slots in the legs.-

cavity type resonators or amplifiers; matching or varying impedance is within the scope of this invention and is contemplated herein. For example, the device may be utilized in matching impedance as well as balancing radio frequency input and will serve for use with other parallel circuits as well as cavity resonator amplifiers. The inventive means may be used .to vary output as well as input. The specific structures and uses are shown by way of example only.

I claim:

1. In an ultra-high frequency'cavity type amplifier, a pair of like electronic tubes, each of said tubes having a grid terminal, an ultra-high frequency input source and means for coupling said input source to said tubes comprising a coupling strap of conductive material connecting said grid terminals, a conductor secured to said input source, and an analyzing arm of conductive material pivotally secured at one end to said conductor, the free end of said analyzing arm being slidably positioned on said coupling strap whereby the free end of said analyzing arm may be selectively disposed in desired position along said coupling strap.

2. A variable impedance for balancing two tubes of a parallel circuit, each said tube provided with an input point, comprising a coupling strap of conductive material fixedly supported at two ends and electrically connected at said ends to said input points of said tubes, insulating material superimposed on said coupling strap,

' a conductor member mounted in spaced relationship to said coupling strap and connected to a source of power, and an analyzing arm of conductive material pivotally secured at one end to said conductor member, the other end of said analyzing arm slidably contacting said insulating material.

3. An input coupling device for balancing the operation of a divided electronic circuit having at least two branches, each consisting of a thermionic tube operating in parallel with each other and each said tube having a grid input connection comprising an impedance path to each said gridinput connection over which radio frequency power is developed, input means supplying radio frequency energy from an external source to each said impedance path, and means to adjust the path length to each said grid input connection relative to the path length to the other said grid input connection, thereby varying the input to each said tube so that the opera tion of each said tube may be controlled, said impedance paths structurally comprising low resistance, flat sheet metal stock of relatively large surface area.

4. The device of claim 3 wherein the means to adjust the path length to each said connection alters each said length simultaneously and in inverse relationship to each other to produce substantially equal outputs from each said tube.

5. A variable impedance comprising a radio frequency input means, a yoke of electrical insulating material formed by two legs connected at one end and secured at said end to said input means, an arcuate coupling strap of conductive material secured to the other ends of said legs, said coupling strap having an arcuate slot therein, an analyzing arm of conductive material pivotally secured to said input means at the apex of said yoke, and locking means on said analyzing arm adjacent the free I end thereof and slidably disposed in said slot whereby the free'end of said analyzing arm may be selectively positioned along said arcuate coupling strap.

6. A variable impedance as defined in claim 5 wherein said yoke and said analyzing arm are secured to said input means by a threaded metallic stud and a cooperating nut formed of electrical insulating material.

7. The device of claim 3 wherein the means to adjust the path length to each said connection is independent of said impedance path length to the other said con- Lnection.

5 cludes a single stationary member, and each of said impedance paths includes a member movable with respect to and in contact with said single stationary member.

References Cited in the file of this patent UNITED STATES PATENTS Strecker Aug. 29, 1933 Hansell Feb. 6, 1934 H-ollmann Sept. 7, 1937 Buschbeck June 28, 1938 10 Brown Mar. 7, 1939 

